The current proposal aims to study neural mechanisms of social learning in healthy adults as a precursor to understanding the impact of mental illnesses on social functioning. Changes in social behavior are often the first symptoms of a striking array of neuropsychiatric disorders. However, whereas disruptions in memory, motor, or emotional functioning are readily recognized as symptoms of more serious underlying conditions, decision-making deficits are often overlooked, particularly in the social domain. Furthermore, there exist few behavioral measures or biomarkers to quantify such deficits, due in part to our limited knowledge of the underlying neural mechanisms and their relation to mental disorders. We do so via a tight integration of computational modeling of goal-directed social behavior, and testing the predictions generated using complementary experimental techniques with both fMRI and focal lesion patients. In particular, we focus on the role of dopamine and interactions between the basal ganglia and frontal cortices, which are together critical for goal-directed behavior and known to be affected in a variety of disorders. First, we will use the model, calibrated on observed behavior, to derive trial-by-trial regressors for use in functional neuroimaging experiments. Second, the estimated parameters of the model themselves can be used to compare across health and diseased groups, or find subtypes of the diseased groups. Finally, the neural correlates and the behavioral estimates can be combined in order to find novel brain-behavior markers of diseases. In this way, we seek to provide a unifying account of goal-directed behavior in both social and non- social settings, which has the potential to lead to development of new ways of classifying mental disorders based on dimensions of observable behavior and neurobiological measures.